This invention relates to the preparation of ceramic materials from silazane polymers with increased ceramic yields. The ceramic materials of this invention are obtained by firing a mixture of a R.sub.3 SiNH-containing silazane polymer and certain boron compounds to an elevated temperature in an inert atmosphere or in a vacuum. The boron compound additives allow for the formation of ceramic materials with increased ceramic yield.
Ceramic materials prepared from R.sub.3 SiNH-containing silazane polymers are known in the art. Gaul in U.S. Pat. No. 4,340,619 (issued July 20, 1982), which is hereby incorporated by reference, prepared ceramic materials by firing at elevated temperatures in an inert atmosphere a R.sub.3 SiNH-containing silazane polymer prepared by contacting and reacting, in an inert, essentially anhydrous atmosphere, chlorine-containing disilanes with disilazanes.
Gaul in U.S. Pat. No. 4,312,970, (issued Jan. 26, 1982), which is hereby incorporated by reference, obtained ceramics by firing a R.sub.3 SiNH-containing silazane polymer, prepared by contacting and reacting an organochlorosilane with a disilazane, at elevated temperatures in an inert atmosphere or in a vacuum.
Cannady in U.S. Pat. No. 4,540,803, issued on Sept. 10, 1985, which is hereby incorporated by reference, prepared ceramic materials from R.sub.3 SiNH-containing silazane polymers which were, in turn, prepared by contacting and reacting trichlorosilane and disilazanes.
What is newly discovered is that certain boron compounds when added to R.sub.3 SiNH-containing silazane polymers prior to firing at elevated temperatures, allow for the formation of ceramic materials with a significant increase in ceramic yield relative to ceramic materials fired under the same conditions without the additives.